MULTIPLE PREGNANCY ASS. PROF. ASS. PROF. Dr. Ahmed Jasim

Definitions In general terms, multiple pregnancy is a pregnancy with two or more fetuses. Twins make up the vast majority (97 – 98%) of multiple gestations. Pregnancies with three or more fetuses are referred to as ‘ higher multiples ’

Prevalence In the UK, twins currently account for approximately 1.5% of all pregnancies. Higher multiples occur in 1 in 2500 pregnancies. Traditionally the expected incidence has been calculated using Hellin ’ s rule. Using this rule, twins were expected in 1 in 80 pregnancies, triplets in 1 in 80 2 and so on.

Risk factors For dizygotic twinning include:  Previous multiple pregnancy  Family history (maternal side)  Increasing maternal age  Racial origin (more common in women of West African ancestry, less common in those of Japanese ancestry)  Assisted conception

Classification The classification of multiple pregnancy is based on: number of fetuses: twins, triplets, quadruplets, etc., number of fertilized eggs: zygosity (dizygotic & monozygotic), number of placentas: chorionicity (dichorionic & monochorionic), number of amniotic cavities: amnionicity (diamniotic & monoamniotic).

Aetiology Dizygotic twins arise from the release of two eggs at ovulation. Monozygotic twins arise from a single fertilized ovum that split into two identical structures

The type of monozygotic twin depends on how long after conception the split occurs: embryo splits at 3 days ---» two chorions, two amnions (DCDA). embryo splits at 3 days ---» two chorions, two amnions (DCDA). embryo splits at 4-7 days ---» single placenta, one chorion, two amnions (MCDA). embryo splits at 8-12 days ---» single placenta, one chorion and one amnion (MCMA) (rare). embryo splits at 13 days ---» conjoined or Siamese twins (very rare)

Physiological changes All the physiological changes of pregnancy (increased cardiac output, volume expansion, relative haemodilution, diaphragmatic splinting, weight gain, lordosis, etc.) are exaggerated in multiple gestations. The ‘ minor ’ symptoms of pregnancy may be exaggerated. For women with pre-existing health problems, such as cardiac disease, a multiple pregnancy may substantially increase their risk of morbidity.

Presentation  Nearly all multiple pregnancies are now diagnosed in the first trimester by ultrasound. However, some twins die and are absorbed in the first half of pregnancy ('the disappearing twin' syndrome) and early scanning increases awareness of this phenomenon.  Early symptoms may include hyperemesis and other exaggerated pregnancy-related symptoms. The uterus may be palpated abdominally earlier than 12 weeks gestation.  In the second half of pregnancy, may present with large- for-dates uterine size, higher than expected weight gain, > 2 fetal poles on palpation and two or more fetal heart rates heard on auscultation.

Management Prenatal diagnosis: Fetal abnormality is more common in multiple pregnancies - both the maternal age specific chromosomal disorders (as increasing maternal age is a risk factor for multiple birth) and fetal anatomical disorders. However there are important difference in both risk and management, based upon chorionicity: Each fetuses of a dichorionic twin pregnancy has a risk of structural anomalies, such as spina bifida, that is similar to that of singleton. Therefore the chance of finding an anomaly within a dichorionic twin pregnancy is twice that of a singleton. Each fetuses of a dichorionic twin pregnancy has a risk of structural anomalies, such as spina bifida, that is similar to that of singleton. Therefore the chance of finding an anomaly within a dichorionic twin pregnancy is twice that of a singleton.

In contrast, each fetus in a monochorionic twin pregnancy carries a risk for abnormalities that is four times that of a singleton. This is presumably due to a higher risk of vascular events during embryonic development. Regarding chromosomal abnormalities, in dizygotic twins, the maternal age – related risk for chromosomal abnormalities for each individual twin remains the same as for a singleton pregnancy. Therefore, at a given maternal age, the chance that at least one of the twin pair is affected by a chromosomal defect is twice as high as for a singleton pregnancy. In monozygotic twin pregnancies, chromosomal abnormalities affect neither fetus or both. The risk is based upon maternal age

Nuchal translucency assessment (ultrasound measurement of the translucency of the nuchal fold in the fetal neck between 10 and 14 weeks) identifies individual fetuses at high risk of trisomy. Nuchal translucency assessment (ultrasound measurement of the translucency of the nuchal fold in the fetal neck between 10 and 14 weeks) identifies individual fetuses at high risk of trisomy. Serum screening is unreliable. Serum screening is unreliable. Invasive prenatal diagnosis (amniocentesis and chorionic villous sampling) is challenging as there are at least 2 fetuses to sample correctly and should be undertaken in a tertiary referral centre. Invasive prenatal diagnosis (amniocentesis and chorionic villous sampling) is challenging as there are at least 2 fetuses to sample correctly and should be undertaken in a tertiary referral centre.prenatal diagnosisprenatal diagnosis If one fetus is detected as abnormal, selective termination (if desired) must be accurately targeted. Selective termination in monochorionic pregnancies risks co-twin sequelae and require different technique. If one fetus is detected as abnormal, selective termination (if desired) must be accurately targeted. Selective termination in monochorionic pregnancies risks co-twin sequelae and require different technique.

Antenatal: Twin pregnancies should be referred to obstetricians for shared care due to the higher risk they present. Twin pregnancies should be referred to obstetricians for shared care due to the higher risk they present. Women should be booked to deliver in a hospital with a SCBU. Women should be booked to deliver in a hospital with a SCBU. Early determination of chorionicity should be routine and this is done most reliably by ultrasound in the late first trimester. In dichorionic twins, there is a V-shaped extension of placental tissue into the base of the inter- twin membrane, referred to as the ‘ lambda ’ or ‘ twin- peak ’ sign. In monochorionic twins, this sign is absent and the inter-twin membrane joins the uterine wall in a T-shape. Early determination of chorionicity should be routine and this is done most reliably by ultrasound in the late first trimester. In dichorionic twins, there is a V-shaped extension of placental tissue into the base of the inter- twin membrane, referred to as the ‘ lambda ’ or ‘ twin- peak ’ sign. In monochorionic twins, this sign is absent and the inter-twin membrane joins the uterine wall in a T-shape.

Assessment of chorionicity later in pregnancy is less reliable and relies upon assessment of fetal gender, number of placentas and the characteristic of the membrane between the two amniotic sacs. The ‘ lambda ’ sign becomes less accurate, and membrane thickness must be utilized. Those twins found to be monochorionic should be scanned frequently to detect twin-twin transfusion or intra-uterine growth retardation at an early stage. If suspected, these pregnancies should be referred to tertiary fetal medicine centres for further management. Assessment of chorionicity later in pregnancy is less reliable and relies upon assessment of fetal gender, number of placentas and the characteristic of the membrane between the two amniotic sacs. The ‘ lambda ’ sign becomes less accurate, and membrane thickness must be utilized. Those twins found to be monochorionic should be scanned frequently to detect twin-twin transfusion or intra-uterine growth retardation at an early stage. If suspected, these pregnancies should be referred to tertiary fetal medicine centres for further management.intra-uterine growth retardationintra-uterine growth retardation

All twin pregnancies (regardless of chorionicity) are regularly scanned after about 30 weeks to monitor growth and fetal well-being with early delivery induced in cases of growth cessation and/or poor Doppler blood flow indices. All twin pregnancies (regardless of chorionicity) are regularly scanned after about 30 weeks to monitor growth and fetal well-being with early delivery induced in cases of growth cessation and/or poor Doppler blood flow indices. Anaemia should be looked for and treated vigorously (many would recommend routine (as opposed to selective) supplementation of folic acid and iron in multiple pregnancy). Anaemia should be looked for and treated vigorously (many would recommend routine (as opposed to selective) supplementation of folic acid and iron in multiple pregnancy). Hospital bed rest in uncomplicated cases is not recommended. Hospital bed rest in uncomplicated cases is not recommended. Maternal complications such as pre-eclampsia are also more common in multiple pregnancies so antenatal carers should be vigilant for early signs. Maternal complications such as pre-eclampsia are also more common in multiple pregnancies so antenatal carers should be vigilant for early signs.pre-eclampsia

Intrapartum: On admission in labour, obtain IV access, blood grouped and saved, monitor fetal heart rates separately and check position of lead fetus: In 60% case both fetuses present as cephalic In 60% case both fetuses present as cephalic In 20% cases 1st twin cephalic, 2nd breech In 20% cases 1st twin cephalic, 2nd breech In 10% cases breech/cephalic In 10% cases breech/cephalic In 10% cases breech/ breech In 10% cases breech/ breech

Vaginal delivery of twins With no complicating factors, the mother can go into spontaneous labour provided the first twin has a cephalic presentation. When the first twin presents transversely, Caesarean section is indicated. When the first twin presents as a breech, clinician usually recommend delivery by elective Ceasarean section. this is largely because of the increased risk associated with singleton breech vaginal delivery. Other factors include dwindling experience of breech delivery and the rarely seen phenomenon of ‘looked twins’ (the chin of the first (breech) baby looked against the chin of the second (cephalic) baby). With no complicating factors, the mother can go into spontaneous labour provided the first twin has a cephalic presentation. When the first twin presents transversely, Caesarean section is indicated. When the first twin presents as a breech, clinician usually recommend delivery by elective Ceasarean section. this is largely because of the increased risk associated with singleton breech vaginal delivery. Other factors include dwindling experience of breech delivery and the rarely seen phenomenon of ‘looked twins’ (the chin of the first (breech) baby looked against the chin of the second (cephalic) baby).Caesarean sectionCaesarean section

The ideal criteria for a twin labour are: Spontaneous onset, Spontaneous onset, Cephalic presentation of twin 1, Cephalic presentation of twin 1, Twin 1 larger than twin 2, Twin 1 larger than twin 2, Dichorionic pregnancy. Dichorionic pregnancy.

With rupture of membranes, check for prolapse of umbilical cord. With rupture of membranes, check for prolapse of umbilical cord. Immediately after the first baby, abdominal palpatrion should be done to determine the lie of the second fetus: Immediately after the first baby, abdominal palpatrion should be done to determine the lie of the second fetus: If longitudinal, rupture the second amniotic sac (once presenting part is engaged, usually after a couple of contractions) and proceed to delivery. If longitudinal, rupture the second amniotic sac (once presenting part is engaged, usually after a couple of contractions) and proceed to delivery. If transverse, external cephalic or internal podalic version may be attempted to bring into longitudinal lie. If successful, as confirmed by vaginal examination, then rupture the second amniotic sac once the fetal head is engaged. If unsuccessful, deliver by Caesarean section. If transverse, external cephalic or internal podalic version may be attempted to bring into longitudinal lie. If successful, as confirmed by vaginal examination, then rupture the second amniotic sac once the fetal head is engaged. If unsuccessful, deliver by Caesarean section.

Contractions can reduce after the birth of the first fetus and if they do not quickly return (within 15 minutes), set up an IV oxytocin infusion following which birth of second fetus should be straightforward. The second twin should deliver within minutes of the first twin. Contractions can reduce after the birth of the first fetus and if they do not quickly return (within 15 minutes), set up an IV oxytocin infusion following which birth of second fetus should be straightforward. The second twin should deliver within minutes of the first twin. Where there are difficulties with the delivery of the second twin or if it develops a bradycardia, a vacuum extraction (in cephalic position) or breech extraction can be performed without necessarily resorting to Caesarean delivery. Where there are difficulties with the delivery of the second twin or if it develops a bradycardia, a vacuum extraction (in cephalic position) or breech extraction can be performed without necessarily resorting to Caesarean delivery. Third stage should be actively managed by IM injection of Syntometrine® or Syntocinon® as the fetal head is being born to avoid postpartum haemorrhage. Third stage should be actively managed by IM injection of Syntometrine® or Syntocinon® as the fetal head is being born to avoid postpartum haemorrhage.postpartum haemorrhagepostpartum haemorrhage Twin deliveries should be attended by 2 paediatricians, 2 obstetricians and an anaesthetist. Twin deliveries should be attended by 2 paediatricians, 2 obstetricians and an anaesthetist.

Complications Although a naturally occurring phenomena, multiple pregnancies are considered high-risk because: Smaller babies - fetuses tend to be individually smaller than those in a singleton pregnancy because of greater demand for nutrients and slower in utero growth i.e. light-for-dates. Monozygotic twins tend to be smaller than dizygotic twins. Smaller babies - fetuses tend to be individually smaller than those in a singleton pregnancy because of greater demand for nutrients and slower in utero growth i.e. light-for-dates. Monozygotic twins tend to be smaller than dizygotic twins. Increased risk of prematurity - the mean gestation for twins is 37 weeks and for triplets 31 weeks. Increased risk of prematurity - the mean gestation for twins is 37 weeks and for triplets 31 weeks.prematurity Higher risk of congenital abnormality associated with multiple pregnancies (x2-4 rate in singleton pregnancies). Higher risk of congenital abnormality associated with multiple pregnancies (x2-4 rate in singleton pregnancies). Higher rates of cerebral palsy found in twins (1-1.5%) and triplets (7-8%). Higher rates of cerebral palsy found in twins (1-1.5%) and triplets (7-8%). Perinatal mortality rate for twins is significantly higher than singletons (x5) and even higher for triplets (x6). Rates are higher for monochorionic twins than dichorionic twins (49 versus 11.5/1000). Perinatal mortality rate for twins is significantly higher than singletons (x5) and even higher for triplets (x6). Rates are higher for monochorionic twins than dichorionic twins (49 versus 11.5/1000).

Higher rate of maternal pregnancy-related complications such as hyperemesis gravidarum, polyhydramnios, pre-eclampsia, anaemia, antepartum haemorrhage. Higher rate of maternal pregnancy-related complications such as hyperemesis gravidarum, polyhydramnios, pre-eclampsia, anaemia, antepartum haemorrhage.hyperemesis gravidarum antepartum haemorrhagehyperemesis gravidarum antepartum haemorrhage Higher rate of complications in labour - malpresentation, cord prolapse, premature separation of placenta, cord entanglement, postpartum haemorrhage. Higher rate of complications in labour - malpresentation, cord prolapse, premature separation of placenta, cord entanglement, postpartum haemorrhage.cord prolapsecord prolapse Also the non-medical financial, social and emotional consequences of caring for twins or higher order multiples need to be kept in mind. Also the non-medical financial, social and emotional consequences of caring for twins or higher order multiples need to be kept in mind.

Complication unique to monochorionic twinning: twin-to-twin transfusion syndrome (TTTS)  In all monochorionic twin pregnancies there are placental vascular anastamoses present which allow communication between the two fetoplacental circulations. In some monochorionic twin pregnancies, imbalance in the flow of blood across these arteriovenous communication result in twin-to-twin transfusion syndrome. The donor twin may become growth restricted and oliguric with oligohydromnios. The recipient fetus become hypervolaemic, leading to polyuria and polyhydramnios. There is a risk of myocardial damage and a high output cardiac failure. It occurs in about 15 percent of twins with a shared placenta.

Complication unique to monoamniotic twinning monoamniotic twin share a single amniotic cavity, with no dividing membrane between the two fetuses. they are at increased risk of cord accident (cord entanglement)

Thank you